A seat belt is the one of the most valuable pieces of safety equipment in your car.
Since 1975, these restraints have prevented nearly 300,000 fatalities, according to the National Highway Traffic Safety Administration. When used properly, lap-and-shoulder belts reduce the risk of fatal injury to front seat occupants by 45 percent.
Seat belts only become more effective when they work in concert with other safety innovations.
Take airbags, for example. That reduction in fatal injury risk among front seat occupants jumps to 51 percent when seat belts and airbags are used together. Frontal airbags saved nearly 40,000 lives from 1987 to 2012, according to the NHTSA.
Statistics like this illustrate why airbags have long-been federally required, and why vehicle manufacturers seem to be adding more and more of them to their vehicles.
Here is a bit more on how airbags work.
What are airbags made of?
In most cases, they’re made from nylon.
How long have they been around?
For more than 40 years. The 1974 model year Oldsmobile Toronado is commonly credited as the first car with passenger airbags.
Where are they located?
Frontal airbags for drivers and passengers have been required in cars, vans and light trucks since the 1999 model year. Side-impact airbags have become increasingly common, though they aren’t mandated. Roof or rollover bags, especially in sport-utility vehicles, are another non-mandated but increasingly available feature.
Generally speaking, it’s common to see as many as six or more airbags in newer vehicles.
How airbags work
Airbag deployment depends on several factors including speed, a vehicle’s rate of deceleration upon impact and the angle of impact. Frontal airbags, according to NHTSA, should deploy in moderate to severe frontal crashes, which means a vehicle has struck the equivalent of a fixed barrier at between 8 and 14 miles per hour.
How does an airbag deploy?
When a crash triggers an airbag sensor to activate, an igniter – a pyrotechnic charge often tied to the vehicle’s electrical system – sets off a chemical reaction that inflates the bag in the blink of an eye. Drivers and passengers often describe smoke following airbag deployments, though this is actually residue of lubricants used during deployment. Traditionally, these are either nontoxic cornstarch or talcum powder.
First responders to a crash, such as paramedics or EMTs, often disable a vehicle’s electrical system to avoid activating airbags.
Deployment happens in the blink of an eye, you say?
It’s actually much quicker than that. Think about it like this: There are 1,000 milliseconds in a second. The internet will tell you the average blink takes between 300 and 400 milliseconds, with some estimates as low as 100 milliseconds.
NHTSA says frontal airbags can deploy in less than 50 milliseconds.
Side airbags are even quicker, deploying in as little as 10 milliseconds, according to the Insurance Institute for Highway Safety.
Wait. Can we go back to that whole pyrotechnic thing?
You bet. The principal chemical used to deploy most airbags is sodium azide. Like a lot of substances, its description, courtesy of the Centers for Disease Control and Prevention, is downright frightening.
“Sodium azide is a rapidly acting, potentially deadly chemical that exists as an odorless white solid. When it is mixed with water or an acid, sodium azide changes rapidly to a toxic gas with a pungent (sharp) odor. It also changes into a toxic gas (hydrazoic acid) when it comes into contact with solid metails,” reads a CDC website.
In a car crash, however, an electrical charge causes sodium azide to straight up explode, which converts it to nitrogen gas that inflates the airbag and protects your face and torso from an unpleasant encounter with your steering wheel or dashboard.
Have some airbags been recalled?
In May, NHTSA announced an expansion and acceleration of Takata airbag inflator recalls, which, according to the agency, have been tied to 11 deaths and 180 injuries in the U.S.
A combination of time, environmental moisture and fluctuating high temperatures contribute to the degradation of ammonium nitrate propellant used in the airbag inflators, wrote NHTSA. This degradation can cause the propellant to burn too quickly, rupturing the inflator module and sending shrapnel through the airbag.
Between May 2016 and December 2019, an estimated 35 to 40 million inflators are expected to be recalled on top of nearly 29 million inflators already recalled.
NHTSA calls the Takata recall the largest and most complex safety recall in U.S. history.
You can check for this and any other recall on your vehicles by visiting SaferCar.gov.
What about my knees – my poor, poor knees!
Knee airbags are among several airbag innovations that have either come to market or seen the light of day as a prototype.
What are smart airbags?
Smart airbags, also known as advanced frontal airbags, are designed to change power depending on the needs of the occupant being protected. They’re linked with seat belts and will typically deploy at lower thresholds for occupants who are not belted in. Smart airbags are often connected with dashboard sensors that indicate whether there is enough pressure, or load, to activate the system.
I’ve heard airbags can be dangerous for little ones.
The force of airbag deployment is one of the biggest reasons not to put young children in the front seat. NHTSA recommends children age 12 and younger ride in the back seat.
Can I reuse an airbag after it deploys?
Nope. That’s a very dangerous idea. Any airbag that has deployed should be replaced by a service technician, and the sooner the better.
To learn more about car parts and how they work, visit AAA.com/Car101.
Written with contribution from AAA’s Car Doctor, John Paul.